Sundials warnings not showing since 7.1.1 upgrade

[dweindl]

Sundials warnings got lost since sundials 7 upgrade (#2513). (Things like Internal t = 2.13327 and h = 1.33227e-16 are such that t + h = t on the next step.).

This is because there are now separate channels for errors and warnings, see https://sundials.readthedocs.io/en/latest/sundials/Logging_link.html#status-and-error-logging.

It's straightforward to redirect the errors, but for the warnings that are handled through SUNLogger it's less convenient. There doesn't seem to be a good way of redirecting warnings - we either need to read them from a file, or create some slightly customized SUNLogger, using sundials' private API and capture some C stream (, or ignore those warnings).

[dweindl]

Oh well, the much simpler solution would be just slightly modifying cvProcessError / IDAProcessError to channel the warnings into the error handler instead of the logger.